Thread: Problem with overloaded operators, templates and inheritance

Hi !

I have a base class and a derived class ( which inherits the base class ).

I want to derived class to overload the [] operator, so that it can perform certain operations and also call the [] operator of the base class. I have used to BaseClass before and I know it isn't the source of the problem. I have abreviated some code with ( ... ) when I felt it was not necessary to put said code.

Here is what I have done so far :

Code :
DerivedClass.h

Code:

template <typename T>
DerivedClass : public BaseClass<T>
{
public :
	...
	...
	...
T &operator[] (int param);
};

DerivedClass.cpp
...
...
...

Code:

template <typename T>
T &DerivedClass<T>::operator[] (int param) 
{
...
...
...
}

Main.cpp

Code:

...
DerivedClass test();
...
test[i] = 12;
...

But I get a Segmentation Fault everytime I run the program.
I have removed all code in the overloaded operator [] in the derived class so I know this is not the problem.
If I call test[i] = 12 I get a segfault even if [] does not have any code in it's implementation.
If I don't call [] I don't have any problems.
I have tried different values, etc. but after some extensive testing I can see the problem is not there.

I have no idea what I could be doing wrong... but I really have close to no experience overloading operators and working with templates so I'm no surprised it's not working.

I would appreciate any help you could give me, thank you in advance !

First of all look at this:

Code:

...
DerivedClass test();
...
test[i] = 12;
...

You have ommited the template argument
this shouldn't compile unless you have some standart template argument in the list (which you haven't...)

anyways heres is a small code of my own:
see if it works for you

Code:

//Test derived_Operator
#include <iostream>
#include <string>
using namespace std;


//declaration:
template<typename T>
class Base 
{
public:
  static const int COUNT = 20;
  Base(){}
  virtual ~Base(){}

  T& operator [] (int iat);
private:
  static T invalid;
  T theMember[COUNT];
};
//implementation:
template<typename T>
T Base<T>::invalid;

template<typename T>
T& Base<T>::operator [] (int iat)
{
  if(iat < COUNT)
    return theMember[iat];
  return invalid;
}

//final Derived class...
template <typename T>
class Derived : public Base <T>
{
public:
  Derived()
  {
  }
  ~Derived()
  {
  }
  string& operator [] (int iat);
private:
  static string error;
  string array[3];
};

template<typename T>
string Derived<T>::error = "ERROR";

template<typename T>
string& Derived<T>::operator[] (int iat)
{
  if(iat < 3)
    return array[iat];
  return error;
}


int main()
{
  Base<int> b;
  Derived<int> d;

  b[0] = 2;
  d[0] = "string no 01";


  cout <<b[0]<<endl<<d[0]<<endl;
}///:~